1. Field of the Invention
The invention relates to a spine fixation apparatus, and more particularly to an enhanced spine fixation apparatus having a compact mechanism adjustable in three dimensions and an enhanced combination.
2. Description of the Prior Art
A spine fixation apparatus is an internal fixation system for fixing at least two vertebrae of the spine for the benefit of promoting recovery of a damaged spine. The spine fixation apparatus is usually made of stainless or special material and is widely used in line with the progress and development of surgical procedures. However, there are still some drawbacks existing in the known various spine fixation apparatuses, such as inconvenience to adjust in an arbitrary direction, damage to soft tissue, and inconvenience to operate. Such drawbacks occur in the light of the fact that the components in a spine fixation apparatus should be properly adjusted so as to conform to the anatomical structure of a patient and to eliminate stress subjected therein. In addition, even if a spine fixation apparatus adjustable in many axes has been developed in the prior art, it includes lots of components and requires a complicated assembly procedure, which in turn places a heavy stress one the surgeon and surgical staff. Also, a long duration for surgery may be required and thus patient morbidity resulting from blood loss and stress of anesthesia may increase.
In U.S. Pat. No. 5,474,551, a spinal fixation device which allows for adjustment in four axes with respect to an attachment of a longitudinal rod to vertebrae of a spinal column is disclosed. However, such a device consists of a multitudes of complicated components and tends to loosen. Moreover, a helical thread is provided on the exterior surface of a distal end of a pedicel screw for coupling other components, such as nut, and thus damage to soft tissue is possible due to exposure of threads after assembly. In U.S. Pat. No. 5,545,163, a spine fixation system comprising an elongated fixation plate is disclosed, in which the position of the plate to be fixed can be selected according to pitches of the pedicel screws. However, the range to be selected is segmental and the orientation of the spine fixation system is not able to be adjusted sufficiently. Further, a helical thread is also provided on the exterior surface of the distal end of a pedicel screw and thus soft tissue damage after assembly is also possible. In U.S. Pat. No. 5,261,910, a pedicel screw provided with a threaded hole at its distal end to couple with a screw is disclosed. However, such a construction fails to allow for an adjustment corresponding to the distance of two pedicel screws and the oblique angles of pedicel screws implanted into the vertebrae. In U.S. Pat. No. 5,735,850, a fastening system for pedicel screws each having a threaded hole at its distal end is disclosed, in which the angle of a connecting member relative to each pedicel screw can be adjusted by the provision of a counter-part capable of sliding against the surface of the connecting member. However, the fixed points of said connecting member cannot be freely selected in so far as to conform to the pitch of two pedicel screws.